U.S. patent application number 16/469716 was filed with the patent office on 2019-11-28 for navigation platform for a medical device, particularly an intracardiac catheter.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Reinardus Gerhardus AARNINK, Harm Jan Willem BELT, Godefridus Antonius HARKS, Frans VENKER.
Application Number | 20190357987 16/469716 |
Document ID | / |
Family ID | 60957283 |
Filed Date | 2019-11-28 |
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United States Patent
Application |
20190357987 |
Kind Code |
A1 |
HARKS; Godefridus Antonius ;
et al. |
November 28, 2019 |
NAVIGATION PLATFORM FOR A MEDICAL DEVICE, PARTICULARLY AN
INTRACARDIAC CATHETER
Abstract
The invention relates to a system for assisting in navigating a
medical device (1) in a region of a patient body, such as a cardiac
chamber. The system comprises a unit (5) for providing a
three-dimensional model of the region and an ultrasound probe (2)
for acquiring image signals of the region of the patient body. At
least one an ultrasound sensor (6) is attached to the medical
device (1) for sensing ultrasound signals emitted by the 5
ultrasound probe (2) and a tracking unit (7) determines a relative
position of the at last one ultrasound sensor (6) with respect to
the live images and/or the ultrasound probe (2) on the basis of the
sensed ultrasound signals. Further, a mapping unit (8) maps the
determined relative position of the at least one ultrasound sensor
(6) onto the model to generate a visualization of region of the
patient body.
Inventors: |
HARKS; Godefridus Antonius;
(Rijen, NL) ; VENKER; Frans; (San Diego, CA)
; BELT; Harm Jan Willem; (Weert, NL) ; AARNINK;
Reinardus Gerhardus; (Best, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
EINDHOVEN |
|
NL |
|
|
Family ID: |
60957283 |
Appl. No.: |
16/469716 |
Filed: |
December 20, 2017 |
PCT Filed: |
December 20, 2017 |
PCT NO: |
PCT/EP2017/083950 |
371 Date: |
June 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62436509 |
Dec 20, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2034/2063 20160201;
A61B 2090/3786 20160201; A61B 2034/2051 20160201; A61M 25/0108
20130101; A61B 2017/00243 20130101; A61B 2090/367 20160201; A61B
34/20 20160201; A61B 2034/2061 20160201; A61B 2090/364 20160201;
A61B 2017/00703 20130101; A61B 2034/105 20160201; A61B 2017/00699
20130101; A61B 2034/2065 20160201; A61B 2090/3784 20160201 |
International
Class: |
A61B 34/20 20060101
A61B034/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2017 |
EP |
17171529.5 |
Claims
1. A system for assisting a user in navigating a cardiac medical
device in a cardiac region of a patient body, the system
comprising: a cardiac medical device, a 3D model providing unit
configured to provide a three-dimensional cardiac model of the
cardiac region of the patient body, an ultrasound probe for
acquiring image signals of the cardiac region of the patient body
and an ultrasound unit configured to provide live images of the
cardiac region of the patient body on the basis of the image
signals, at least one ultrasound sensor attached to the cardiac
medical device for sensing ultrasound signals emitted by the
ultrasound probe, a tracking unit configured to determine a
relative position of the at last one ultrasound sensor with respect
to the live images and/or the ultrasound probe on the basis of the
sensed ultrasound signals, and a mapping unit configured to map the
determined relative position of the at least one ultrasound sensor
onto the cardiac model to generate a visualization of the cardiac
region of the patient body on the basis of the cardiac model and on
the basis of the result of the mapping.
2. The system as defined in claim 1, wherein the mapping unit is
configured to generate a visualization of the cardiac model in
which the position of the at least one ultrasound sensor is
marked.
3. The system as defined in claim 2, wherein the mapping unit is
configured to map the live images onto the cardiac model and to
overlay the cardiac model with the live images in the
visualizations on the basis of the result of this mapping.
4. The system as defined in claim 3, wherein the mapping unit is
configured to map the live images onto the cardiac model on the
basis of an image comparison of the live images and the cardiac
model.
5. The system as defined in claim 3, wherein the mapping unit is
configured to map the live images onto the cardiac model on the
basis of a relative position and orientation of the ultrasound
probe with respect to a reference frame associated with the cardiac
model.
6. The system as defined in claim 5, wherein the 3D model providing
unit is configured to create the cardiac model using ultrasound
images acquired using the ultrasound probe during an initialization
phase in which a further ultrasound sensor is positioned at a
reference position and wherein the reference frame is defined on
the basis of a relative position and orientation of the ultrasound
probe with respect to the further ultrasound sensor determined on
the basis of the ultrasound signals sensed by the further
ultrasound sensor.
7. The system as defined in claim 5, wherein the further ultrasound
sensor is positioned at the reference position during the
acquisition of the live images and wherein the mapping unit is
configured to determine the relative position and orientation of
the ultrasound probe with respect to the reference frame on the
basis of the relative position and/or orientation of the further
ultrasound sensor with respect to the ultrasound probe.
8. The system as defined in claim 1, wherein the cardiac region of
the patient body undergoes a periodic motion having different
motion phases, wherein the cardiac model is a dynamic model
comprising a deforming sub-model for each of the motion phases and
wherein the mapping unit is configured to determine a current
motion phase and to map the relative position of the at least one
ultrasound sensor on the deforming sub-model for the current motion
phase.
9. The system as defined in claim 1, wherein the cardiac medical
device is configured to carry out electrical measurements to
generate an electro-anatomical map of the cardiac region of the
patient body and wherein the mapping unit is configured to overlay
the electro-anatomical map over the cardiac model on the basis of
the relative position of the at least one ultrasound sensor with
respect to the ultrasound probe during the measurements.
10. The system as defined in claim 1, wherein the mapping unit is
configured to generate a visualization of the cardiac model
corresponding to a view as seen by view of a virtual eye based on
the position of the at least one ultrasound sensor.
11. The system as defined in claim 10, wherein the mapping unit is
configured to map the live images onto the view and to overlay the
view with the live image in the visualization on the basis of the
result of the mapping.
12. The system as defined in claim 10, wherein the mapping unit is
configured to generate the visualization on the basis of a mapping
of the live image and/or the position and orientation of the
ultrasound probe onto the model and on the basis of the relative
position and orientation of the at least one ultrasound sensor with
respect to the ultrasound probe.
13. The system as defined in claim 1, wherein the ultrasound probe
is configured to emit ultrasound signals into different directions
and wherein the tracking unit is configured to determine the
position of the at least one ultrasound sensor based on a reception
level of the ultrasound signals in the ultrasound sensor and/or
wherein the tracking unit is configured to determine the position
of the at least one ultrasound sensor on the basis of a time
difference between the emission of the ultrasound signals by the
ultrasound probe and their sensing by the ultrasound sensor.
14. A method for assisting a user in navigating a cardiac medical
device having at least one an ultrasound sensor attached thereto in
a cardiac region of a patient body, the method comprising:
providing a three-dimensional cardiac model of the cardiac region
of the patient body, obtaining receiving live images of the cardiac
region of the patient body on the basis of image signals acquired
using an ultrasound probe, determining a relative position of the
at least one an ultrasound sensor attached to the cardiac medical
device with respect to the ultrasound probe, the ultrasound sensor
sensing ultrasound signals emitted by the ultrasound probe, mapping
the determined relative position of the at least one ultrasound
sensor onto the cardiac model to generate a visualization of the
cardiac region of the patient body on the basis of the cardiac
model and on the basis of the result of the mapping.
15. A computer program comprising program code for instructing a
computer device to perform a method as defined in claim 14, when
the computer program is executed on the computer device.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a system and a method for assisting
a user in navigating a medical device in a region of a patient
body. Moreover, the invention relates to a computer program for
carrying out the method. The region of the patient body may
particularly be a cardiac chamber and the medical device may
particularly be an intracardiac catheter or another intracardiac
device.
BACKGROUND OF THE INVENTION
[0002] Interventional cardiology procedures, including
electrophysiology (EP) and structural heart disease (SHD)
procedures rely on the use of fluoroscopy that allows real-time
visualization of the anatomy and of radiopaque devices used in
these procedures. The major disadvantage of fluoroscopy is however
the exposure of the patient and staff to radiation doses.
Therefore, there is a trend and desire to minimize the use of
fluoroscopy during these procedures. Another disadvantage of
fluoroscopy is the inability to visualize soft-tissue
structures.
[0003] Ultrasound (US) imaging is also often used in these
procedures, including intracardiac echocardiography (ICE),
transesophageal echocardiography (TEE) and transthoracic
echocardiography (TTE). US imaging has the advantage that it allows
for the visualization of soft-tissue structures and blood flow
without harmful scatter radiation. Devices such as catheters and
needles can be visualized using ultrasound. However, it is often
difficult to identify the tip of such a device, in particular when
using two-dimensional ultrasound, because the device can be out of
the imaged plane and because shadowing and reverberations
complicate the identification of the tip.
[0004] Navigation platforms for navigating medical devices in
cardiology procedures therefore may use additional hardware for
tracking the medical device in accordance with a certain tracking
modality such as electromagnetic (EM) tracking, impedance tracking,
optical shape sensing or satellite-based tracking. However, these
tracking modalities give rise to inaccuracies with respect to the
localization of medical device relative to the anatomy as e.g.
shown in the US images.
[0005] Likewise, if the tracked devices are used to reconstruct the
anatomy of the heart or another body region as in
electro-anatomical mapping, for example, the generated
representation of the anatomy may be inaccurate due to inaccuracies
in the tracking of the devices. In EM tracking, such inaccuracies
may particularly be due to metal in the environment which can cause
disturbances. For impedance tracking, patches on the patient
surface are used as reference but inhomogeneities in impedances for
various tissues (e.g. cardiac and lung) and changes in volume load
during the procedure can create inaccuracies. For optical shape
sensing, a fixture at the patient table is used as a reference and
the position error of this fixture propagates over the length of
the optical fiber. For satellite-based tracking, such as tracking
using the Global Positioning System (GPS), also the localization is
independent of anatomy.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
navigation platform that mitigates the aforementioned problems and
allows for a more accurate localization of a medical device with
respect to the anatomy as shown in US images thereof.
[0007] In accordance with a first aspect, the invention provides a
system for assisting a user in navigating a medical device in a
region of a patient body. The system comprises: (i) a 3D model
providing unit configured to provide a three-dimensional model of
the region of the patient body, (ii) an ultrasound probe for
acquiring image signals of the region of the patient body and an
ultrasound unit configured to provide live images of the region of
the patient body on the basis of the image signals, (iii) at least
one ultrasound sensor attached to the medical device for sensing
ultrasound signals emitted by the ultrasound probe, (iv) a tracking
unit configured to determine a relative position of the at last one
ultrasound sensor with respect to the live images and/or the
ultrasound probe on the basis of the sensed ultrasound signals, and
(v) a mapping unit configured to map the determined relative
position of the at least one ultrasound sensor onto the model to
generate a visualization of the region of the patient body on the
basis of the model and on the basis of the result of the
mapping.
[0008] Since the position of the medical device is tracked by
determining the relative position of the at least one ultrasound
sensor with respect to the ultrasound probe on the basis of the
ultrasound signals emitted by the ultrasound probe and sensed by
the ultrasound sensor, it is possible to accurately track the
medical device in relation to the anatomy of the region of the
patient body as imaged by means of the ultrasound probe. Further,
the position of the ultrasound sensor and, thus, of the medical
device can be displayed in relation to a model of the relevant
region of the patient body. This is done on the basis of the
mapping of the position onto the model, which particularly
corresponds to a transformation of the position into a reference
frame in which the model is defined.
[0009] In one embodiment, the mapping unit is configured to
generate a visualization of the model in which the position of the
at least one ultrasound sensor is marked. In a related embodiment,
the mapping unit is further configured to map the live images onto
the model and to overlay the model with the live images in the
visualizations on the basis of the result of this mapping. In these
embodiments, it is possible to visualize the position and/or
orientation of the medical device with respect to the anatomy as
represented by the model and, optionally, also with respect to the
live images. On the basis of these visualizations, the medical
device can be accurately steered within the region of the patient
body.
[0010] In a further related embodiment, the mapping unit is
configured to map the live images onto the model on the basis of an
image comparison of the live images and the model. The image
comparison may particularly be carried out on the basis of fiducial
features in the live images and corresponding features of the
model. On the basis of the image comparison, the live images can be
mapped onto the model relatively quickly and easily.
[0011] In a further embodiment, the mapping unit is configured to
map the live images onto the model on the basis of a relative
position and orientation of the ultrasound probe with respect to a
reference frame associated with the model. It is an advantage of
this embodiment that the mapping on the basis of the position and
orientation information allows for a very accurate matching of the
live images and the model.
[0012] In the mapping procedure, the position information may be
taken into consideration in addition to the comparison of the live
images and the model in order to improve the accuracy of the
mapping. Likewise, it is possible to carry out the mapping on the
basis of the comparison or on the basis of the position and
orientation information alone.
[0013] In a one embodiment, the 3D model providing unit is
configured to create the model using ultrasound images acquired
using the ultrasound probe during an initialization phase in which
a further ultrasound sensor is positioned at a reference position
and the reference frame is defined on the basis of a relative
position and orientation of the ultrasound probe with respect to
the further ultrasound sensor determined on the basis of the
ultrasound signals sensed by the further ultrasound sensor. A
related embodiment includes that the further ultrasound sensor is
positioned at the reference position during the acquisition of the
live images and that the mapping unit is configured to determine
the relative position and orientation of the ultrasound probe with
respect to the reference frame on the basis of the relative
position and/or orientation of the further ultrasound sensor with
respect to the ultrasound probe.
[0014] In these embodiments, the further ultrasound sensor may be
attached to a further medical device. This medical device may be
held a fixed position during the initialization phase and during
the procedure, in which the position of the aforementioned at least
one ultrasound sensor is tracked, so that the position of the
further ultrasound sensor mounted on the device can be used in the
aforementioned way as a position reference. In exemplary
implementations of these embodiments, the further medical device
may specifically be used in order to provide a position reference.
In alternative implementations, the further medical device may have
another function during the procedure. An example of such a further
medical device is a diagnostic electrophysiology (EP) catheter
which may be used for sensing electrical signals or for applying
electrical signals to tissue for stimulation.
[0015] Likewise, it is possible to track the ultrasound probe
independently of the position of a further ultrasound sensor. In
this respect, one embodiment includes that the system further
comprises a tracking arrangement for determining the position and
orientation of the ultrasound probe with respect to the reference
frame, the tracking arrangement using at least one tracking
technique from the group comprising electromagnetic tracking,
impedance tracking, optical shape sensing and satellite-based
tracking.
[0016] The he region of the patient body may undergo a periodic
motion having different motion phases. In this respect, one
embodiment includes that the model is a dynamic model comprising a
deforming sub-model for each of the motion phases and that the
mapping unit is configured to determine a current motion phase and
to map the relative position of the at least one ultrasound sensor
on the deforming sub-model for current motion phase. This allows
for generating visualizations for different phases of the periodic
motion of the region of the patient body. The periodic motion of
the region of the patient body may be due to cardiac motion and/or
due to respiratory motion. The current motion phases may be
identified on the basis of the live ultrasound images Likewise,
other techniques may be applied to identify the motion phases.
[0017] In a further embodiment, the medical device is configured to
carry out electrical measurements to generate an electro-anatomical
map of the region of the patient body and wherein the mapping unit
is configured to overlay the electro-anatomical map over the model
on the basis of the relative position of the at least one
ultrasound sensor with respect to the ultrasound probe during the
measurements. The electro-anatomical map may particularly comprise
an activation map and/or a voltage map of the region of the patient
body which may include a region of the patient's heart. By
generating the electro-anatomical map on the basis of the position
information determined using the at least one ultrasound sensor, an
accurate map of the relevant region of the patient body can be
determined.
[0018] In a further embodiment, the mapping unit is configured to
generate a visualization of the model corresponding to a view as
seen by a virtual eye based on the position of the at least one
ultrasound sensor. The virtual eye may particularly be located at
the position of the at least one ultrasound sensor. In such a way
the anatomy of the relevant region of the patient body can be
viewed from the point of view the ultrasound sensor which may
particularly be attached to the tip of the medical device. In
further implementations of these embodiments, the virtual eye may
be positioned at the location of a certain anatomical landmark
presented in the three-dimensional model.
[0019] The view as seen by the virtual eye particularly comprises
parts of the model which are included in a field of view of the
virtual eye. The field of view of the virtual eye may particularly
be directed along the longitudinal direction of the distal end
section of the medical device in this case and cover a region in
front of the medical device.
[0020] In a related embodiment, the mapping unit is configured to
map the live images onto the view and to overlay the view with the
live image in the visualization on the basis of the result of the
mapping. In a further related embodiment, the mapping unit is
configured to generate the visualization on the basis of a mapping
of the live image and/or the position and orientation of the
ultrasound probe to the model and on the basis of the relative
position and orientation of the at least one ultrasound sensor with
respect to the ultrasound probe.
[0021] With respect to the determination of the relative position
of the at least one ultrasound sensor with respect to the
ultrasound probe, one embodiment includes that the ultrasound probe
is configured to emit ultrasound signals into different directions
and that the tracking unit is configured to determine the position
of the at least one ultrasound sensor based on a reception level of
the ultrasound signals in ultrasound sensor. In a further
embodiment, the tracking unit is configured to determine the
position of the at least one ultrasound sensor on the basis of a
time difference between the emission of the ultrasound signals by
the ultrasound probe and their sensing by the ultrasound
sensor.
[0022] In accordance with a further aspect, the invention provides
a method for assisting a user in navigating a medical device in a
region of a patient body. The method comprises: (i) providing a
three-dimensional model of the region of the patient body, (ii)
obtaining live images of the region the patient body on the basis
of image signals acquired using an ultrasound probe, (iii)
determining a relative position of at least one an ultrasound
sensor attached to the medical device with respect to the
ultrasound probe, the ultrasound sensor sensing ultrasound signal
emitted by the ultrasound probe, (iv) mapping the determined
relative position of the at least one ultrasound sensor onto the
model to generate a visualization of the region of the patient body
on the basis of the model and on the basis of the result of the
mapping.
[0023] In accordance with a further aspect, the invention provides
a computer program comprising program code for instructing a
computer device to perform the method, when the computer program is
executed on the computer device.
[0024] It shall be understood that the system of claim 1 and the
method of claim 14 and the computer program of claim 15 have
similar and/or identical preferred embodiments, in particular, as
defined in the dependent claims.
[0025] It shall be understood that a preferred embodiment of the
present invention can also be any combination of the dependent
claims or above embodiments with the respective independent
claim.
[0026] These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In the following drawings:
[0028] FIG. 1 schematically and exemplarily shows components of a
system for navigating a medical device in a region of a patient
body,
[0029] FIG. 2 schematically and exemplarily shows a
three-dimensional model of a left atrium of a heart,
[0030] FIG. 3a schematically and exemplarily shows a
two-dimensional slice corresponding to a field of view of an US
probe of the system, which is mapped onto the model,
[0031] FIG. 3b schematically and exemplarily shows a
three-dimensional cone corresponding to a field of view of an US
probe of the system, which is mapped onto the model,
[0032] FIG. 4 schematically and exemplarily shows a visualization
in which a live US-image and a position of the medical device is
overlaid over the model,
[0033] FIG. 5 schematically and exemplarily shows on overlay of a
current position and preceding positions of an US sensor attached
to the medical device over the model,
[0034] FIG. 6 schematically and exemplarily shows steps of a
procedure for generating visualizations in which a position of a
medical device is shown using a model.
DETAILED DESCRIPTION OF EMBODIMENTS
[0035] FIG. 1 schematically and exemplarily shows components of a
system for navigating a medical device 1 in a region of a patient
body, which may particularly correspond to a cardiac chamber. The
system allows for visualizing the relevant region of the patient
body and a position and/or orientation of one or more medical
device(s) 1 used in the region of the patient body to a physician
performing an interventional procedure using the medical device. On
the basis of the generated visualizations, the physician can steer
the medical device 1 during the interventional procedure.
[0036] The medical device 1 may be a catheter, particularly an
ablation catheter, a needle or a guidewire, for example. The system
may particularly be used for carrying out structural heart disease
procedures including valve replacement/repair (e.g. Transcatheter
Aortic Valve Replacement (TAVR), mitraclip, pulmonic valve,
tricuspid valve etc.) and occlusions (e.g. ASD/PFO closure, VSD
closure, left atrial appendage closure, etc.). Moreover, the system
may be used in electrophysiology (EP) studies with ablation,
including catheter ablation procedure for treatment of arrhythmias
including atrial fibrillation (AF).
[0037] The system comprises a miniaturized US probe 2 which
includes an US transducer for emitting US signals and for sensing
echoes of the US signals in order to generate US images with
respect to a certain field of view. During the interventional
procedure, the US probe 2 is inserted into the patient body to
acquire live US images of the relevant body region essentially in
real-time. In order to insert the US probe 2 into the patient body,
it may be attached to a catheter or a similar elongated device.
[0038] The US probe 2 is configured to acquire three- or
two-dimensional US images. In order to the generate the US images,
the US signals sensed by means of the US probe 2 are processed in a
US unit 3 which is located external to the patient body and
connected to the US probe 2 and which is configured to generate the
US images on the basis of US signals in a manner known to the
person skilled in the art as such.
[0039] In case the relevant region of the patient body includes a
cardiac chamber, the US probe 2 is preferably inserted into the
heart to image the relevant cardiac chamber in accordance with an
ICE technique. However, the US probe 2 may likewise be configured
and utilized in accordance with another echocardiography technique
known to a person skilled in the art, such as echocardiographic
imaging from the esophagus as in TEE or echocardiographic imaging
from a position external to the patient body as in TTE.
[0040] Moreover, the system comprises a tracking arrangement for
determining the position and/or orientation of the medical device 1
relative to the US probe 2. This tracking arrangement will be
described in more detail further below. On the basis of the
relative position and/or orientation of the medical device 1 with
respect to the US probe 2, the system generates the visualization
of the position and/or orientation of the medical device 1 in the
relevant region of the patient body.
[0041] In the system, the visualization of the relevant region of
the patient body and of the position and/or orientation of the
medical device 1 positioned therein is based on a three-dimensional
model of the relevant region of the patient body. More
specifically, the system may generate visualizations in which the
live US images and indications of the position and/or orientation
of the medical device are overlaid over the model. In addition or
as an alternative, the system may generate visualizations which
include a part of the model included in the field of view of a
virtual eye at the tip of the medical device 1. This part of the
model may further be overlaid by the live US images in the
visualizations.
[0042] For displaying the visualizations of the volume of interest
and of the position and/or orientation of the medical device 1, the
system further comprises a display unit 4. The display unit 4 may
comprise a monitor screen. Likewise, the display unit 4 may be
configured in another way and may comprise virtual reality glasses,
for example.
[0043] The three-dimensional model of the relevant region of the
patient is preferably created prior to the actual interventional
procedure during which the live US images are acquired and stored
in a 3D model providing unit 5 for use during the actual
interventional procedure. By way of example, a corresponding model
21 of the left atrium of the heart is schematically illustrated in
FIG. 2.
[0044] In one implementation, the model is created on the basis of
a series of US images acquired using the US probe 2 during an
initialization phase preceding the actual interventional procedure.
During this initialization phase, the US probe 2 may be moved to
image relevant region of the patient body essentially completely in
a series of US images. Then, the 3D model providing unit 5 may
create the model by combining the US images, particularly by
stitching the US images. For this purpose, any stitching technique
known the person skilled in the art may be applied.
[0045] If the relevant region of the patient body comprises the
left atrium of the heart, as it is the case in ablation of atrial
fibrillation (AF), for example, it may be imaged from the right
atrium through the interatrial septum. For this purpose, the US
probe 2 is placed at an appropriate position in the right atrium
and is operated to acquire a series of US images of the left atrium
under different viewing angles so that the left atrium is imaged
essentially completely. On the basis of these images, a model of
the left atrium may then be created in the 3D model providing unit
5 by stitching the acquired US images. As an alternative, the US
probe 2 may be positioned within the left atrium for acquiring the
series of images of the left atrium under different viewing angles.
For this purpose, a transseptal puncture can be made in order to
cross the interatrial septum with the US probe 2. In this
procedure, a sufficiently small US probe 2 may be used which allows
for a safe transseptal crossing. In order to acquire images of the
complete left atrium, the US probe 2 may be moved in a suitable
combination of translations, deflections and rotations.
[0046] During the acquisition of the series of images used for
creating the model, the positions and orientation of the US probe 2
may optionally be tracked with respect to a certain reference frame
in order to determine the position and orientation of the model in
this reference frame. As will be explained further below, the
position and orientation may be used in the process of mapping the
live US images onto the model. For tracking the position and
orientation of the US probe 2, any suitable tracking technique
known to a person skilled in the art may be used. Examples of such
tracking techniques include a tracking on the basis of images of
the relevant region of the patient body acquired using a suitable
imaging modality, such as fluoroscopy, or EM tracking, impedance
tracking, optical shape sensing and satellite-based tracking.
[0047] In accordance with a further approach, the position and
orientation of the US probe 2 may be tracked relative to the
position and orientation of a further medical device in a manner
further described below, when the further medical device, which is
also referred to a reference device herein below, is positioned at
a fixed reference location during the initialization phase and
during the actual interventional procedure. In this case, the
reference device defines the reference frame for the tracking of
the US probe 2.
[0048] In further implementations, the model of the relevant body
region of a particular patient may be selected from a plurality of
pre-generated models for the same body region, which may be
generated on the basis of data collected for other patients and
stored in a corresponding library. These models may likewise be
created on the basis of US image data. Alternatively, these models
may be created on the basis of imaging data of another imaging
modality, such as computed tomography (CT imaging) or magnetic
resonance (MR) imaging. From the pre-generated models, one model
may be selected which best matches with the anatomy of the
patient.
[0049] The selection of the best matching model may again be
carried out on the basis of US images acquired during an
initialization phase. In particular, the model may be selected,
which has the largest similarity to the US images in accordance
with the suitable similarity measure. The similarities between an
US image and the model may be determined on the basis of a
segmented version of the US image, which may be computed using a
suitable procedure known the person skilled in the art. The
similarity measure may be computed on the basis of the number of
overlapping points between the segmented US image and the model for
the best overlap between the segmented US image and the model. On
the basis of the determined position and orientation of the US
probe 2 at the time of the acquisition of the US images, the
position and orientation of the selected model in a reference frame
may again be determined as described above.
[0050] In further alternatives, the three-dimensional model may be
created on the basis of images of the relevant body region which
are not acquired using the US probe 2 but using another imaging
modality. For instance, in case the US probe 2 is an ICE probe, the
images may be acquired using another US imaging modality, such as
TEE or TTE Likewise, another imaging modality may be used to
acquire one or more image(s) for creating the model, such as, for
example computed tomography (CT) imaging, magnetic resonance (MR)
imaging or 3D rotational angiography (3DATG). Also in these
implementations, the position and orientation of the model in a
reference frame may be determined, e.g. by tracking the utilized US
probe or on the basis of the known image frame of the CT or MR
image.
[0051] Further, when the relevant body region moves periodically
during the interventional procedure, as it is particularly the case
if the relevant body region includes a cardiac chamber, the
three-dimensional model of the relevant body region may represent
the body region in one particularly phase of its periodic motion.
In this implementation, visualizations may only be generated for
the relevant motion phase. This particularly means that only live
US images and position and/or orientation information acquired
during the relevant motion phase are used in the system. These data
may be selected on the basis of a gating signal, which indicates
the start and end of the relevant motion phase in each cycle of the
periodic motion.
[0052] In case the relevant body region includes a cardiac chamber,
the relevant motion phase may correspond to the systole or the
diastole. The gating signal may be derived from an
electrocardiography (ECG) signal for, example. As an alternative,
any other signal varying in synchronization with the periodic
motion of the heart may be used. So, the gating signal may be
derived from position and/or orientation information of the US
probe 2 and/or the tracked medical device 1. Likewise, the gating
signal may be derived from the live US images acquired by means of
the US probe 2. In this embodiment, a statistical property of the
live US images varying in synchronization with the period motion of
the heart, such as the mean pixel value (in case of two-dimensional
images) or voxel value (in case of three-dimensional images) or the
variance of all pixel or voxel values, may be evaluated, and the
gating signal may be derived from the variations of this
property.
[0053] Moreover, a gating mechanism may be applied with respect to
other motions of the heart, such as respiratory motion. In this
case, the model of the heart may be created for a particular phase
of the respiratory motion of the heart, and only live US images and
position and/or orientation information acquired during this phase
are used in the system for generating a visualization. For
determining the occurrence of the relevant phase of the respiratory
motion, the system may further comprise a sensor for determining
the respiratory motion, such as, for example, a sensor for
determining the ventilation air flow and/or a sensor for
determining the movement of the patient's chest or abdominal wall
during breathing. On the basis of the signals of this sensor, the
data including the live US images and the position and/or
orientation data are unlocked (for the relevant phase of the
respiratory motion) or locked (during other phases of the
respiratory motion) for the creation of visualizations.
[0054] As an alternative to a static model and the aforementioned
gating, a dynamic model may be used. This model may include
deforming sub-models for each relevant phase of the periodic motion
of the relevant body region, where of each deforming sub-model
models the changing form of the relevant body region. These
sub-models may be defined on the basis of vector fields describing
the displacement of image portions of the model with time during
the motion phases. In each of the motion phases, the system uses
the associated sub-model for generating the visualizations on the
basis of live US images and position and/or orientation information
for the tracked medical device 1 acquired during this motion phase.
Corresponding sub-models may be created for different phases of the
cardiac motion and/or for the respiratory motion of the relevant
body region.
[0055] For identifying the relevant motion phases in this
alternative, suitable trigger signals are used, which may be
derived in a similar manner as the aforementioned gating signals.
In case the relevant region of the patient body includes a cardiac
chamber, the trigger signals may particularly again be derived from
an ECG signal or from another signal varying in synchronization
with the heart motion. Optionally, the dynamic model may also be
generated for different phases of the respiratory motion of the
heart and the corresponding phases may be identified using a sensor
for determining the respiratory motion.
[0056] In the way described above, models of various regions of
interest may be created. One such region may be the left atrium as
described above. In a similar manner, models can particularly be
created for other heart chambers, such as the right atrium, left
and right ventricle, or for vessels such as the aorta, pulmonary
artery, pulmonary veins, inferior vena cava, superior vena cava,
coronary arteries, coronary veins, or for a valve anatomy, such as
the aortic valve, mitral valve, tricuspid valve, pulmonary valve,
or the esophagus.
[0057] The tracking arrangement for determining the position and/or
orientation of the medical device 1 relative to the US probe 2
includes at least one US sensor 6 attached to the medical device 1,
particularly to its tip. The US sensor 6 is configured to sense US
signals incident onto the US sensor 6. For this purpose, the US
sensor 6 may comprise a foil of US sensitive material. Likewise,
the US sensor 6 may comprise an US transducer, such as for example,
a lead zirconium titanate (PZT) transducer, a single crystal
transducer (SXL), a capacitive micro-machined ultrasonic transducer
(CMUT) or a piezoelectric micro-machined ultrasonic transducer
(PMUT), where only the ability to sense US signals is used here.
During operation in the present system, the US sensor 6 senses US
signals emitted by the US probe 2.
[0058] The US sensor 6 is connected to a tracking unit 7 which
determines the relative position of the US sensor 6 with respect to
the US probe 2 on the basis of the sensed US signals and, thus,
determines the relative position of the tip of the medical device 1
with respect to the US probe 2. In order to determine the
orientation of the medical device 1, at least one further US sensor
6 is attached to the medical device 1 and the tracking unit 6 also
determines the relative position of the further US sensor 6 with
respect to the US probe 2 on the basis of the US signals sensed by
the further US sensor 6. On the basis of the relative positions of
the US sensors 6, the tracking unit then determines the orientation
of the medical device 1.
[0059] In order to ascertain the position of one US sensor 6, the
tracking unit 7 evaluates the US signals sensed by the US sensor 6
while the US probe 2 images the volume of interest by emitting US
beam pulses under different azimuth angles and, in case of a 3D US
probe 2, also under different elevation angles. In order to
determine the angular position of the US sensor 6 with respect to
the US probe, the tracking unit 7 compares the responses to the
emitted US beams sensed by the US sensor 6 and determines the
azimuth angle and, in case of a 3D US probe 2, also the elevation
angle under which the beam(s) resulting in the maximum response(s)
have been emitted. The determined angle(s) define(s) the relative
angular position of the US sensor 6 with respect to the US probe 2.
The distance between the US sensor 6 and the US probe 2 is
determined on the basis of the time delays between the times of the
transmission of the beams producing the maximum responses and the
times of the sensing of the beams by the US sensor 6, i.e. on the
basis of the time of flight of the beams.
[0060] Exemplary implementations of this tracking technique are
also described in WO 2011/138698A1 and in the publication "A New
Sensor Technology for 2D Ultrasound-Guided Needle Tracking",
Huanxiang Lu et al, MICCAI 2014, Part II, LNCS 8674, pp. 389-396,
2014. In the present system, the tracking technique may be
implemented in a similar manner.
[0061] As said above, in one embodiment the system generates
visualizations in which the live US images and indications of the
position and/or orientation of the medical device 1 are overlaid
over the model of the relevant region of the patient body. These
visualizations are displayed at the display unit 4 during an
interventional procedure in order to assist the physician in
steering the medical device 1 during the interventional
procedure.
[0062] In order to generate these visualizations, a mapping unit 8
of the system maps the live US images acquired using the imaging
probe 2 onto the model of the relevant region of the patient body
provided by the 3D model providing unit 5. Thus, the mapping unit 8
determines the part of the model which is included in the live
images. In FIG. 3a, this mapping is schematically and exemplarily
illustrated for a two-dimensional slice 31 corresponding to a field
of view of an US probe 2 for acquiring two-dimensional images,
which is mapped onto the model 21 of the left atrium shown in FIG.
2. FIG. 3b schematically and exemplarily illustrated the mapping
for a three-dimensional cone 32 corresponding to a field of view of
an US probe 2 for acquiring three-dimensional images, which is
mapped onto the model 21 of the left atrium shown in FIG. 2.
[0063] In one implementation, the mapping of a live US image onto
the model is performed on the basis of the comparison between the
live US image and the model. In particular, an image registration
between the live US image and the model may be carried out which
involves the determination of a rigid transformation for
transforming the US image such that it matches a portion of the
model. The rigid transformation comprises a rotation and/or a
translation.
[0064] In one embodiment of the registration procedure, the mapping
unit 8 may identify fiducial image points in the live US image and
map these image points to corresponding points of the model in
order to determine the transformation. The mapping of fiducial
points can be carried out using known computer vision techniques,
such as, for example, scale-invariant feature transform (SIFT).
Alternatively, a registration method may be applied which
determines the rigid transformation such that the transformed live
US image has the largest similarity to the model. Such a
registration procedure may be performed on the basis of a segmented
version of the live US image, which may be determined using a
suitable segmentation procedure known the person skilled in the
art. The similarity between the (transformed) US image and the
model may again be determined on the basis of a suitable similarity
measure, e.g. as explained above.
[0065] In case the model is a dynamic model, the mapping of the
live US image onto the model may also be made by matching estimated
motion vectors describing the displacement of image portions in the
live image pertaining to one motion phase relative to the positions
of the image portions in a live image of the preceding motion phase
with the motion vectors describing the displacement of image
portions of the dynamic model.
[0066] The mapping of the live US images onto the model may be
performed on the basis of the aforementioned image registration
procedure alone. In this case, the determined transformation may
also be evaluated to determine the relative position of the US
probe 2 with respect to the model, i.e. in the reference frame in
which the model is defined.
[0067] In addition or as an alternative, the mapping of a live US
image onto the model may be performed on the basis of information
about the position and orientation of the US probe 2 in case the
position and orientation of the model has been determined with
respect to a reference frame as explained above. Using this
position and orientation information, the mapping unit 8 may
determine a rigid transformation for transforming the live US image
into the reference frame in which the model is defined and maps the
live US image onto the model by applying this transformation. The
transformation may be determined on the basis of the information
about position and orientation of the US probe 2 alone or it may be
determined based on this information and additionally based on an
image registration between the live US image and the model as
explained above.
[0068] In order to carry out the mapping in this embodiment, the
position and orientation of the US probe 2 at the time of the
acquisition of the live image within the reference frame is
determined. On this basis, the mapping unit 8 further determines
the relative position and orientation of the field of view of the
US probe 2 with respect to the model and uses this information for
determining which part of the model is imaged by the US probe 2 in
the live US image.
[0069] The determination of the position and orientation of the US
probe 2 with respect to the reference frame may be made using any
of the tracking techniques already referred to above in connection
with the description of the creation of the model. Thus, it may be
determined on the basis of images of the relevant body region
acquired using a suitable imaging modality, such as fluoroscopy, or
on the basis of EM tracking, impedance tracking, optical shape
sensing or satellite-based tracking.
[0070] Further, as described above, the position and orientation of
the US probe 2 may likewise be tracked with respect to the
reference device when the reference device is held at the same
fixed position during the initialization phase in which the model
is created and during the actual interventional procedure. In this
implementation, the position and orientation of the reference
device defines the reference frame of the model.
[0071] For determining the relative position and orientation of the
US probe 2 with respect to the reference device during the
initialization phase (for creating the model) and during the
interventional procedure (for generating visualizations of the
basis of the model), the reference device may be equipped with US
sensors and on the basis of the US signals sensed by the US
sensors, the relative position and orientation of the US probe 2
and the reference device is determined as explained above in
connection with the medical device 1. On the basis of this
information, the position and orientation of the US probe 2
relative to the model is determined.
[0072] The reference device may be specifically provided in order
to establish a reference position and orientation for the tracking
of the US probe 2. Alternatively, the reference device may be a
medical device which has another function during the interventional
procedure but is substantially not moved during the procedure, such
as, for example, a diagnostic EP catheter for sensor electrical
signals or applying electrical signals to tissue for
stimulation.
[0073] Upon having mapped the live US image onto the model, the
mapping unit 8 may create a visualization in which the live US
image is overlaid over the model in accordance with the result of
the mapping. Further, the mapping unit 8 marks the position(s) of
the US sensor(s) 6 attached to the medical device 1 in the
visualization, i.e. in the live US image and the model as included
in the visualization. The marking may be made by placing
corresponding dots or other symbols in the visualization. The
visualization is then displayed at the display unit 4 of the
system. A corresponding visualization is schematically and
exemplarily illustrated in FIG. 4 for a three-dimensional US image
41. In the example illustrated in FIG. 4, the medical device 1 is
shown in the US image and the position of an US sensor 6 attached
to the tip of the medical device 1 is marked with a dot 42.
[0074] In order to mark the position(s) of the US sensor(s) 6 in
the visualization, the mapping unit 8 determines the relative
position(s) of the US sensor(s) 6 attached to the medical device 1
with respect to live US image and/or the model.
[0075] This may be done on the basis of the relative position(s) of
the US sensor(s) 6 with respect to the US probe 2 as determined in
the tracking unit 7 and on the basis of the relative position of
the US probe 2 or the live US image acquired using the US probe 2
with respect to the model. These data allow for determining the
relative position(s) of the US sensor(s) 6 with respect to the
model so that the mapping unit 8 can place the marks in the
visualization accordingly.
[0076] Likewise, the mapping unit 8 may directly determine the
position(s) of the US sensor(s) 6 in the model. This is
particularly possible if the position and orientation of the
medical device 1 defines the reference frame of the model as
describe above.
[0077] In one implementation, the mapping unit 8 generates the
visualizations in such a way that each of the visualizations shows
the current position(s) of the US sensor(s) attached to the medical
device 1, i.e. the position(s) at the time of the acquisition of
the live US image included in the visualization. Thus, a physician
viewing the visualization at the display unit can easily determine
the current position and/or orientation of the medical device 1
during the interventional procedure.
[0078] In a further implementation, the mapping unit 8 may generate
the visualizations in such a way that previous positions of the one
or more of the US sensor(s) 6 attached to the medical device 1 are
marked in addition to the current position(s). By way of example, a
corresponding visualization is illustrated in FIG. 5. In this
visualization, the current position of a US sensor 6 attached to a
medical device 1 is indicated by means of a mark 51 in the model 21
of the left atrium and previous positions of the US sensor are
indicated by means of marks 52a-c.
[0079] In particular, the visualizations may be generated such that
previous positions of the US sensor 6 attached to the device's tip
are additionally marked in the visualizations. This is particularly
useful if the medical device 1 is an ablation catheter. In this
case, the previous positions may correspond to previous ablation
points. These points may be identified manually or automatically
during the ablation procedure and stored in the mapping unit 8 in
response to their identification so that they can be marked in
subsequently generated visualizations. In addition, also ablation
parameters such as power and duration, which were used for ablation
at the ablation points, or lesion parameters may be stored in the
mapping unit 8 and displayed in connection with the marks
identifying the ablations points in the visualizations.
[0080] In addition or as an alternative to the previous positions
of the US sensor 6, the system may mark positions of a planned
(future) trajectory of the medical device 1 in the presented
visualization in order to assist the physician viewing the
visualizations in following the planned trajectory.
[0081] In a further embodiment, the mapping unit 8 generates
visualizations for displaying at the display unit 4, which comprise
a part of the model included in the view of a virtual eye at the
location of the US sensor 6 attached to the tip of the medical
device 1. The field of view of the virtual eye may particularly be
directed along the longitudinal direction of the distal end section
of the medical device 1 and cover a region in front of the medical
device 1. The visualization may be generated from the
three-dimensional model and optionally also from the live US
images.
[0082] In this embodiment, the mapping unit 8 maps the position and
orientation of the medical device 1 on the model. This mapping is
performed on the basis of a mapping of plural US sensors 6 attached
to the medical device 1 on the model. The latter mapping is carried
out directly or on the basis of the mapping of the position and
orientation of the US probe 2 onto the model and on the basis of
the relative positions of the US sensors 6 with respect to the US
probe 2 as already described above. On the basis of the mapping of
the position and orientation of the medical device 1 onto the
model, the mapping unit 8 then determines the parts of the model
which are included in the field of view of the virtual eye and
generates the visualization such that it includes these parts in a
view which corresponds to the view as seen by the virtual eye.
[0083] In addition, the mapping unit 8 may map the live US images
acquired by means of the US probe 2 onto the determined view of the
model on the basis of a transformation of the US image. For this
purpose, the mapping unit 8 may determine a rigid transformation
for transforming the image space corresponding to the live US image
to a new image space corresponding to the field of view of the
virtual eye on the basis of the relative position and orientation
of the medical device 1 with respect to the US probe 2. This
transformation is then applied to the live US image. Thereupon, the
mapping unit 8 generate a visualization in which the transformed
live US image is overlaid over the model.
[0084] In such a way it is possible to visualize the anatomy of the
relevant region of the patient body from the point of view of the
tip of the medical device 1. Such visualization can further assist
a physician in steering the medical device 1 during the
interventional procedure. In this respect, the embodiments
described above can also be combined such that it is possible to
switch between a visualization in which the positions of the US
sensors are marked 6 in the overlay of the live US images on the
model and a visualization corresponding to the view as seen by the
virtual eye.
[0085] In the system described above, particularly the US unit 3,
the 3D model providing unit 5, the tracking unit 7 and the mapping
unit 8 may be implemented as software modules executed on one or
more computer device(s). For this purpose, a corresponding computer
program is provided and installed on the computer device(s), which
comprises instructions for executing the functions of the units.
Further, the computer device(s) is/are particularly connected to
the US probe 2 and the US sensor(s) 6 in order to control the
operation of the US probe 2 and to receive US signals acquired by
the US probe 2 and the US sensor(s) 6. Moreover, the computer
device(s) is/are connected to the display unit 4 to control the
display unit 4 to display the generated visualizations as explained
above.
[0086] In the embodiments of the system described above, it is
possible to generate visualizations of a model and live US images
of a region of the patient body on the basis of the position and/or
orientation of one medical device 1 included in the relevant region
of the patient body, where the position(s) of US sensor(s) 6
attached to the medical device 1 are marked in the visualizations
or where the visualizations correspond to the view as seen by a
virtual eye at the location of a US sensor 6 attached to the tip of
the medical device 1.
[0087] In FIG. 6, some of the steps of the related procedure are
summarized. In the illustrated step 61, the three-dimensional model
of the relevant region of the patient body is generated in the
initialization phase as explained above. Thereupon, during the
actual interventional procedure, live US images are acquired by
means of the US probe 2 (step 62). Further, the relative
position(s) of the US sensor(s) 6 attached to the medical device 1
and the US probe 2 is/are determined as explained above (step 63).
These positions are mapped onto the model 21 by the mapping unit 8
(step 64). Moreover, the mapping unit 8 generates a visualization
as described above in which the positions of the US sensor(s) are
marked in the model 21 (step 65). In addition, the mapping unit may
map the live US images acquired by means of the US probe onto the
model 21 (step 66) and overlay the live US images over the model 21
accordingly in the generated visualization.
[0088] In a similar manner, it is also possible to generate
corresponding visualizations with respect to a plurality of medical
devices 1 used in the relevant region of the patient body.
[0089] In related embodiments, the positions of US sensors 6
attached to these medical devices 1 may all be marked in the
visualizations and/or the mapping unit 8 may generate
visualizations corresponding to views as seen by virtual eyes at
the locations of the tips of the different medical devices 1. In
the latter case, it may also be possible to switch between these
visualizations. Moreover, the mapping unit 8 may mark in the
visualization pertaining to one medical device 1 the positions of
US sensor 6 attached to the other medical devices 1 if they are
included in the field of view of the virtual eye at the tip of the
relevant medical device 1. The corresponding marks may be
positioned on the basis of a mapping of the positions of the US
sensors 6 onto the field of view of the virtual eye.
[0090] Further, one embodiment of the system comprises that the
medical device 1 is an EP catheter which is used for generating an
electro-anatomical map of the relevant region of the patient body,
such as a cardiac chamber. This map may be overlaid over the
aforementioned visualizations generated in the system on the basis
of the model and may include an activation map indicating local
activation times and/or a voltage map indicating local electrogram
amplitudes. The EP catheter may comprise a plurality of electrodes
for sensing electrical signals and optionally for delivering
stimulation signals and on the basis of the sensed electrical
signals, local activation times and/or electrogram amplitudes are
determined in a way known to a person skilled in the art. For
generating the activation and/or voltage map, the EP catheter is
moved within the relevant region of the patient body and local
measurements are made at different locations within the region. At
each measurement location, the positions of the electrodes are
determined on the basis of the US signals sensed by means of the US
sensor(s) 6 attached to the EP catheter as explained above. Then,
the results of the local measurements are combined to generate the
map and the mapping unit 8 may overlay the map onto the model of
the relevant region of the patient body on the basis of the
recorded position ad orientation information.
[0091] Moreover, the generated visualizations may be fused with
fluoroscopy images of the relevant region of the patient body
acquired using a fluoroscopy device.
[0092] Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims.
[0093] In the claims, the word "comprising" does not exclude other
elements or steps, and the indefinite article "a" or "an" does not
exclude a plurality.
[0094] A single unit or devices may fulfill the functions of
several items recited in the claims. The mere fact that certain
measures are recited in mutually different dependent claims does
not indicate that a combination of these measures cannot be used to
advantage.
[0095] A computer program may be stored/distributed on a suitable
medium, such as an optical storage medium or a solid-state medium,
supplied together with or as part of other hardware, but may also
be distributed in other forms, such as via the Internet or other
wired or wireless telecommunication systems.
[0096] Any reference signs in the claims should not be construed as
limiting the scope.
* * * * *